Transition metal atom (M)-encapsulating silicon cage
nanoclusters
(M@Si16) exhibit a superatomic nature, depending on the
central M atom owing to the number of valence electrons and charge
state on organic substrates. Since M@Si16 superatom featuring
group 4 and 5 transition metal atoms exhibit rare-gas-like and alkali-like
characteristics, respectively, group 6 transition metal atoms are
expected to show alkaline earth-like behavior. In this study, M@Si16, comprising a central atom from group 6 (MVI =
Cr, Mo, and W) were deposited on C60 substrates, and their
electronic and chemical stabilities were investigated in terms of
their charge state and chemical reactivity against oxygen exposures.
In comparison to alkali-like Ta@Si16, the extent of charge
transfer to the C60 substrate is approximately doubled,
while the oxidative reactivity is subdued for MVI@Si16 on C60, especially for W@Si16. The
results show that a divalent state of MVI@Si162+ appears on the C60 substrate, which is consistently
calculated to be a symmetrical cage structure of W@Si162+ in C3v, revealing insights into the “periodic law” of M@Si16 superatoms pertaining to the characteristics of alkaline
earth metals.